The present invention relates to a tool for tightening and slackening a driven threaded member possessing a polygonal driven profile, of the type comprising an active head, the cross-section of which has a roughly polygonal shape.
The invention applies both to female tools intended to drive a male nut and to male tools intended to drive a screw, the head of which has a polygonal recess.
Available tools possess approximately polygonal profiles which are symmetrical with respect to the two directions of rotation. Consequently, a given stress experienced by the tool corresponds to both the same torque and the same stress applied to the driven member, whether in the direction of tightening or in that of slackening.
More specifically, the many profiles provided for tightening/slackening tools (commercial names: Snap-On, Facom, Kaynar, Wera, Kevalar, etc.) are aimed at obtaining as Judicious a compromise as possible between, on the one hand, the stress induced in the male element and, on the other hand, the stress for bursting the female profile, especially when the latter is the profile of the tool.
Now, in practice, the conditions to be complied with are not generally the same in both directions of rotation. For example, it is absolutely essential to protect a nut which is being tightened, whereas it is often acceptable to damage an obstinate nut which is being untightened, for example if it is rusty or jammed, provided that it is successfully untightened.
Moreover, it may be necessary, in certain cases, to be able to develop, with a given tool, a tightening torque markedly greater than the usual tightening torques.